SPEERMINT Working Group S. Niccolini
Internet-Draft NEC
Intended status: Informational E. Chen
Expires: January 15, 2009 NTT
J. Seedorf
NEC
July 14, 2008
SPEERMINT Security Threats and Suggested Countermeasures
draft-niccolini-speermint-voipthreats-04
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Abstract
This memo presents the different security threats related to
SPEERMINT classifying them into threats to the Location Function, to
the Signaling Function and to the Media Function. The different
instances of the threats are briefly introduced inside the
classification. Finally the existing security solutions in SIP and
RTP/RTCP are presented to describe the countermeasures currently
available for such threats. The objective of this document is to
identify and enumerate the SPEERMINT-specific threat vectors in order
to specify security-related requirements. Once the requirements are
identified, methods and solutions how to achieve such requirements
can be selected.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Security Threats relevant to SPEERMINT . . . . . . . . . . . . 5
2.1. Threats Relevant to the Look-Up Function (LUF) . . . . . . 5
2.1.1. Threats to LUF Confidentiality . . . . . . . . . . . . 5
2.1.2. Threats to LUF Integrity . . . . . . . . . . . . . . . 5
2.1.3. Threats to LUF Availability . . . . . . . . . . . . . 5
2.2. Threats Relevant to the Location Function (LF) . . . . . . 6
2.2.1. Threats to LF Confidentiality . . . . . . . . . . . . 6
2.2.2. Threats to LF Integrity . . . . . . . . . . . . . . . 6
2.2.3. Threats to LF Availability . . . . . . . . . . . . . . 6
2.3. Threats to the Signaling Function (SF) . . . . . . . . . . 7
2.3.1. Threats to SF Confidentiality . . . . . . . . . . . . 7
2.3.2. Threats to SF Integrity . . . . . . . . . . . . . . . 7
2.3.3. Threats to SF Availability . . . . . . . . . . . . . . 8
2.4. Threats to the Media Function (MF) . . . . . . . . . . . . 9
2.4.1. Threats to MF Confidentiality . . . . . . . . . . . . 9
2.4.2. Threats to MF Integrity . . . . . . . . . . . . . . . 9
2.4.3. Threats to MF Availability . . . . . . . . . . . . . . 10
3. Suggested Countermeasures . . . . . . . . . . . . . . . . . . 11
3.1. Security Requirements . . . . . . . . . . . . . . . . . . 11
3.2. Database Security . . . . . . . . . . . . . . . . . . . . 11
3.3. DNSSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.4. DNS Replication . . . . . . . . . . . . . . . . . . . . . 12
3.5. Cross-Domain Privacy Protection . . . . . . . . . . . . . 12
3.6. Digest Authentication on all requests in peering
agreements . . . . . . . . . . . . . . . . . . . . . . . . 12
3.7. Use TCP instead of UDP to deliver SIP messages . . . . . . 12
3.8. Ingress Filtering / Reverse-Path Filtering . . . . . . . . 12
3.9. Strong Identity Assertion . . . . . . . . . . . . . . . . 13
3.10. Reliable Border Element Pooling . . . . . . . . . . . . . 13
3.11. Rate limit . . . . . . . . . . . . . . . . . . . . . . . . 13
3.12. Border Element Hardening . . . . . . . . . . . . . . . . . 14
3.13. SRTCP . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4. Mapping suggested countermeasures to threats . . . . . . . . . 15
4.1. Current Deployment of Countermeasures . . . . . . . . . . 16
5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 17
6. Security Considerations . . . . . . . . . . . . . . . . . . . 18
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
8. Informative References . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
Intellectual Property and Copyright Statements . . . . . . . . . . 23
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1. Introduction
With VoIP, the need for security is compounded because there is the
need to protect both the control plane and the data plane. In a
legacy telephone system, security is a more valid assumption.
Intercepting conversations requires either physical access to
telephone lines or to compromise the Public Switched Telephone
Network (PSTN) nodes or the office Private Branch eXchanges (PBXs).
Only particularly security-sensitive organizations bother to encrypt
voice traffic over traditional telephone lines. In contrast, the
risk of sending unencrypted data across the Internet is more
significant (e.g. DTMF tones corresponding to the credit card
number). An additional security threat to Internet Telephony comes
from the fact that the signaling is sent using the same network as
the multimedia data; traditional telephone systems have the signaling
network separated from the data network. This is an increased
security threat since a hacker could attack the signaling network and
its servers with increased damage potential (call hijacking, call
drop, DoS attacks, etc.). Therefore there is the need of
investigating the different security threats, to extract security-
related requirements and to highlight the solutions how to protect
from such threats.
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2. Security Threats relevant to SPEERMINT
This section enumerates potential security threats relevant to
SPEERMINT. A taxonomy of VoIP security threats is defined in
[refs.voipsataxonomy]. Such a taxonomy is really comprehensive and
takes into account also non-VoIP-specific threats (e.g. loss of
power, etc.). Threats relevant to the boundaries of layer-5 SIP
networks are extracted from such a taxonomy and mapped to the
classification relevant for the SPEERMINT architecture as defined in
[refs.speermintarch], moreover additional threats for the SPEERMINT
architecture are listed and detailed under the same classification
and according the CIA (Confidentiality, Integrity and Availability)
triad:
o Look-Up Function (LUF);
o Location Function (LF);
o Signaling Function (SF);
o Media Function (MF).
2.1. Threats Relevant to the Look-Up Function (LUF)
This is one of the latest additions of the terminology draft
[I-D.ietf-speermint-terminology]. LUF is vulenrable to the same
threats that affect database systems in general.
2.1.1. Threats to LUF Confidentiality
o SIP URIs and peering domains harvesting - an attacker can exploit
this weakness if the underlying database has a weak authentication
system, and then use the gained knowledge to launch other kind of
attacks.
2.1.2. Threats to LUF Integrity
The underlying database could be vulnerable to:
o Injection attack - an attacker could manipulate statements
performed on the database by the end user.
2.1.3. Threats to LUF Availability
The underlying database could be vulnerable to:
o Denial of Service attacks - e.g. an attacker makes incomplete
requests causing the server to create an idle state for each of
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them causing memory to be exhausted.
2.2. Threats Relevant to the Location Function (LF)
2.2.1. Threats to LF Confidentiality
o URI harvesting - the attacker harvests URIs and IP addresses of
the existing User Endpoints (UEs) by issuing a multitude of
location requests. Direct intrusion against vulnerable UEs or
telemarketing are possible attack scenarios that would use the
gained knowledge.
o SIP device enumeration - the attacker discovers the IP address of
each intermediate signaling device by looking at the Via and
Record-Route headers of a SIP message. Targeting the discovered
devices with subsequent attacks is a possible attack scenario.
2.2.2. Threats to LF Integrity
Bogus information can be accepted by LF if specific flaws are
exploited (e.g. if the LF involves a Location Server, LS, that does
not correctly validate routing data such as NAPTR records, then the
LS may develop incorrect Session Establishment Data, SED). Dynamic
call routing discovery and establishment, as in scope of SPEERMINT,
introduces new opportunities for such an attack. In the following
two example variants of such an attack are listed.
o Man-in-the-Middle attack - the attacker has already or inserts an
unauthorized node in the signaling path modifying the SED. The
results is that the attacker is then able to read, insert and
modify the multimedia communications.
o Incorrect destinations - the attacker redirect the calls to a
incorrect destination with the purpose of establishing fraud
communications like voice phishing or DoS attacks.
2.2.3. Threats to LF Availability
The LF can be object of DoS attacks. DoS attacks to the LF can be
carried out by sending a large number of queries to the LS or Session
Manager, SM, with the result of preventing an originating SSP from
looking up call routing data of any URI outside its administrative
domain. As an alternative the attacker could target the DNS to
disable resolution of SIP addresses.
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2.3. Threats to the Signaling Function (SF)
Signaling function involves a great number of sensitive information.
Through signaling function, user agents (UA) assert identities and
VSP operators authorize billable resources. Correct and trusted
operations of signaling function is essential for service providers.
This section discusses potential security threats to the signaling
function to detail the possible attack vectors.
2.3.1. Threats to SF Confidentiality
SF traffic is vulnerable to eavesdropping, in particular when the
data is moved across multiple SSPs having different levels of
security policies. Threats for the SF confidentiality are listed
here:
o call pattern analysis - the attacker tracks the call patterns of
the users violating his/her privacy (e.g. revealing the social
network of various users, the daily phone usage, etc.), also rival
SSPs may infer information about the customer base of other SSPs
in this way;
o Password cracking - challenge-response authentication mechanism of
SIP is not secure if the attacker is able to eavesdrop a
sufficient number of SIP authentication messages exchanged between
a SIP server and a SIP client.
2.3.2. Threats to SF Integrity
The integrity of the SF can be violated using SIP request spoofing,
SIP reply spoofing and SIP message tampering.
2.3.2.1. SIP Request Spoofing
Most SIP request spoofing require first a SIP message eavesdropping
but some of the them could be also performed by guessing or
exploiting broken implementations. Threats in this category are:
session tear down - the attacker uses CANCEL/BYE messages in order
to tear down an existing call at SIP layer, it is needed that the
attacker replicates the proper SIP header for the hijacking to be
successful (To, From, Call-ID, CSeq);
REGISTER spoofing - the attacker forges a REGISTER request and
register a bogus contact information with the objective of
hijacking incoming calls.
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Billing fraud - the same attack as in the case of the REGISTEr
spoofing may lead an attacker to be able to direct billing for
calls to the victim UE and avoid paying for the phone calls;
user ID spoofing - SSPs are responsible for asserting the
legitimacy of user ID; if an SSP fails to achieve the level of
identity assertion that the federation it belongs expects, it may
create an entry point for attackers to conduct user ID spoofing
attacks.
2.3.2.2. SIP Reply Spoofing
Threats in this category are:
Forget 200 Response - the attacker sends a forged CANCEL request
to terminate a call in progress tricking the terminating UE to
believe that the originating UE actually sent it, and successfully
hijacks a call sending a forged 200 OK message to the originating
UE communicating the address of the rogue UE under the attacker's
control;
Forget 302 Response - the attacker sends a forged "302 Moved
Temporarily" reply instead of a 200 OK, this enables the attack to
hijack the call and to redirect it to any destination UE of his
choosing;
Forget 404 Response - the attacker sends a forged "404 Not Found"
reply instead of a 200 OK, this enables the attack to disrupt the
call establishment;
2.3.2.3. SIP Message Tampering
This threat involves the alternation of important field values in a
SIP message or in the SDP body. Examples of this threat could be the
dropping or modification of handshake packets in order to avoid the
establishment of a secure RTP session (SRTP). The same approach
could be used to degrade the quality of media session by letting UE
negotiate a poor quality codec.
2.3.3. Threats to SF Availability
o Flooding attack - a SBE is susceptible to message flooding attack
that may come from interconnected SSPs;
o Session Black Holing - the attacker (assumed to be able to make
Man-in-the-Middle attacks) intentionally drops essential packets,
e.g. INVITEs, to prevent certain calls from being established;
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o SIP Fuzzing attack - fuzzing tests and software can be used by
attackersto discover and exploit vulnerabilities of a SIP entity,
this attack may result in crashing SIP entity.
2.4. Threats to the Media Function (MF)
The Media function (MF) is responsible for the actual delivery of
multimedia comunication between the users and carries sensitive
information. Through media function, UE can establish secure
communications and monitor quality of conversations. Correct and
trusted operations of MF is essential for privacy and service
assurance issues. This section discusses potential security threats
to the MF to detail the possible attack vectors.
2.4.1. Threats to MF Confidentiality
The MF is vulnerable to eavesdropping in which the attacker may
reconstruct the voice conversation or sensitive information (e.g.
PIN numbers from DTMF tones). SRTP and ZRTP are vulnerable to bid-
down attacks, i.e. by selectively dropping key exchange protocol
packets may result in the establishment of a non-secure
communications.
2.4.2. Threats to MF Integrity
Both RTP and RTCP are vulnerable to integrity violation in many ways:
o Media Hijack - if an attacker can somehow detect an ongoing media
session and eavesdrop a few RTP packets, he can start sending
bogus RTP packets to one of the UEs involved using the same codec.
As illustrated in Fig. 8, if the bogus RTP packets have
consistently greater timestamps and sequence numbers (but within
the acceptable range) than the legitimate RTP packets, the
recipient UE may accept the bogus RTP packets and discard the
legitimate ones.
o Media Session Tear Down - the attacker sends bogus RTCP BYE
messages to a target UE signaling to tear down the media
communication, please note tha tRTCP messages are normally not
authenticated.
o QoS degradation - the attacker sends wrong RTCP reports
advertising more packet loss or more jitter than actually
experimented resulting in the usage of a poor quality codec
degrading the overall quality of the call experience.
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2.4.3. Threats to MF Availability
o Malformed messages - the attacker tries to cause a crash or a
reboot of the DBE/UE by sending RTP/RTCP malformed messages;
o Messages flooding - the attacker tries to exhaust the resources of
the DBE/UE by sending many RTP/RTCP messages.
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3. Suggested Countermeasures
This section describes implementer-specific countermeasures against
the threats described in the previous section to supplement the
security requirements described in [I-D.ietf-speermint-requirements].
These countermeasures are described in this section and then mapped
to threats in the following section, indicating which countermeasure
is recommended to be used in order to solve which threat.
3.1. Security Requirements
The security requirements for SPEERMINT have been moved from an
earlier version of this draft to the requirements draft for speermint
[I-D.ietf-speermint-requirements]. These security requirements are
the following [I-D.ietf-speermint-requirements]:
o The protocols used for the LUF and LRF must allow the look-up and
SED data to be exchanged securely (authentication and encryption
services should be provided).
o One or more Certificate Authorities (CAs) should be agreed between
SSPs for securing session peering exchanges. Alternatively, self-
signed certificates may also be used.
o It is recommended that the establishment of media security be
provided along the media path and not over the signaling path
given the indirect peering use cases.
3.2. Database Security
Adequate security measures must be applied to the LUF to prevent it
from being target of attacks since it involves the use of common
database systems. Common security Best Current Practises (BCPs) for
database systems include replication to prevent any database from
being a single point of failure, and the use of parameterized
statements to prevent SQL injections. [refs.dbsec] is one of many
existing literatures that describe BCPs in this area.
3.3. DNSSEC
In the case DNS is used by the LF, it is recommended to deploy the
recent version of Domain Name System Security Extensions (informally
called "DNSSEC-bis") defined by [RFC4033] [RFC4034] [RFC4035], to
permit authentication and data integrity checking of DNS data.
DNSSEC adds new records to the DNS data which permit the validation
of data in the DNS using strong cryptography.
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3.4. DNS Replication
DNS replication is a very important countermeasure to mitigate
availability threats. Attacking multiple DNS servers simultaneously
with the purpose of bringing them all them is much more challenging
than attacking a sole DNS server (single point of failure).
3.5. Cross-Domain Privacy Protection
Stripping Via and Record-Route headers, replacing the Contact header,
and even changing Call-IDs are the mechanisms described in [RFC3323]
to protect SIP privacy. This practice allows an SSP to hide its SIP
network topology, prevents intermediate signaling equipment from
becoming the target of DoS attacks, as well as protects the privacy
of UEs according to their preferences.
3.6. Digest Authentication on all requests in peering agreements
In today's current practice, Digest authentication [RFC2617] is used
to challenge only REGISTER and INVITE requests. However, the more
messages it is applied to the more prevention from threats is
assured. It is recommended to apply digest authentication to all SIP
requests in peering agreements, including BYE and CANCEL, to prevent
attacks such as session tear-down.
3.7. Use TCP instead of UDP to deliver SIP messages
SIP clients need to stay connected with the server on a persistent
basis (differently from HTTP clients). Scalability requirements are
therefore much more stringent for a SIP server than for a web server.
This leads to the choice of UDP as protocol used between SSPs to
carry SIP messages (especially for providers with a large user
community). New improvements in the Linux kernel
[refs.tcp-scalability] show a big increase of the scalability of TCP
in handling large number of persistent (but idle) connections.
Therefore SSP operators still using UDP for their SIP network should
consider switching to TCP. This would increase the difficulty of
performing attacks such as session teardown or forged responses.
Since look-up and SED data should be exchanged securely (see security
requirements), it is further recommended to not only use TCP but TLS
for messages exchanged between SSPs.
3.8. Ingress Filtering / Reverse-Path Filtering
Ingress filtering, i.e., blocking all traffic coming from a host that
has a source address different than the addresses that have been
assigned to that host (see [RFC2827]) can effectively prevent UEs
from sending packets with a spoofed source IP address. This can be
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achieved by reverse-path filtering, i.e., only accepting ingress
traffic if responses would take the same path.
3.9. Strong Identity Assertion
"Caller ID spoofing" can be achieved thanks to a Weak identity
assertion on the From URI of an INVITE request. In a single SSP
domain, strong identity assertion can be easily achieved by
authenticating each INVITE request. However, in the context of
SPEERMINT, only the originating SSP is able to verify the identity
directly. In order to overcome this problem there are currently only
two major approaches: transitive trust and cryptographic signature.
The transitive trust approach builds a chain of trust among different
SSP domains. One example of this approach is a combined mechanism
specified in [RFC3324] and [RFC3325]. Using this approach in a
transit peering network scenario, the terminating SSP must establish
a trust relationship with all SSP domains on the path, which can be
seen as an underlying weakness. The use of cryptographic signatures
is an alternative approach. "SIP Authenticated Identity Body (AIB)"
is specified in [RFC3893]. [RFC4474] introduces two new header
fields IDENTITY and IDENTITY-INFO that allow a SIP server in the
originating SSP to digitally sign an INVITE request after
authenticating the sending UE. The terminating SSP can verify if the
INVITE request is signed by a trusted SSP domain. Although this
approach does not require the terminating SSP to establish a trust
relationship with all transit SSPs on the path, a PKI infrastructure
is assumed to be in place.
3.10. Reliable Border Element Pooling
It is advisable to implement reliable pooling on border elements. An
architecture and protocols for the management of server pools
supporting mission-critical applications are addressed in the
RSERPOOL WG. Using this mechanisms (see [RFC3237] for requirements)
a UE obtains support for server failover in case of availability
problems.
3.11. Rate limit
Packet flooding attacks can be mitigated by limiting the rate of
incoming traffic through policing or queuing. In this way legitimate
clients can be denied of the service since their traffic may be
discarded. Rate limiting can also be applied on a per-source-IP
basis under the assumption that the source IP of each attack packet
is not spoofed dynamically and will all the limitations related to
NAT and mobility issues. It may be preferable to limit the number of
concurrent 'sessions', i.e., ongoing calls instead of the messaging
associated with it (since session use more resources on backend-
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systems). When calculating rate limits all entities along the
session path should be taken into account. SIP entities on the
receiving end of a call may be the limiting factor (e.g., the number
of ISDN channels on PSTN gateways) rather than the ingress limiting
device.
3.12. Border Element Hardening
To prevent attackers from hacking SPEERMINT border elements these
implementations should be seurity hardened. For instance, fuzz
testing is a common black box testing technique used in software
engineering. Also, security vulnerability tests can be carried out
preventively to assure a UE/SBE/DBE can handle unexpected data
correctly without crashing. [RFC4475] and [refs.protos] are examples
of torture test cases specific for SIP devices and freely available
security testing tools, respectively. These type of tests needs to
be carried out before product release and in addition throughout the
product life cycle.
3.13. SRTCP
Secure RTCP (SRTCP) provides the same security-related features to
RTCP as SRTP does for RTP. SRTCP is described in [RFC3711] as
optional. In order to prevent some of the RTCP threats previously
described it is recommended to turn this feature on.
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4. Mapping suggested countermeasures to threats
The following table shows how to mitigate threats with the
appropriate countermeasures listed in section Section 3.
+---------------------------------------------------------+
| Group | Threat | Suggested Countermeasure |
+--------+------------------------------------------------+
| | Unauthorized access | database BCPs |
| +---------------------+--------------------------+
| LUF | SQL injection | database BCPs |
| +---------------------+--------------------------+
| | DoS to LUF | database BCPs |
+--------+---------------------+--------------------------+
| | URI harvesting | DNSSEC |
| +---------------------+--------------------------+
| | SIP equipment | DNSSEC, |
| | enumeration | privacy protection |
| +---------------------+--------------------------+
| LF | MitM attack | DNSSEC |
| +---------------------+--------------------------+
| | Incorrect | |
| | destinations | DNSSEC |
| +---------------------+--------------------------+
| | DoS to LF | DNS replication |
+--------+---------------------+--------------------------+
| | Call pattern | |
| | analysis | TLS |
| +---------------------+--------------------------+
| | Password cracking | TLs |
| +---------------------+--------------------------+
| | Session Tear Down | TLS, TCP, digest auth. |
| +---------------------+--------------------------+
| | REGISTER spoofing | digest auth. |
| +---------------------+--------------------------+
| | Billing fraud | digest auth. |
| +---------------------+--------------------------+
| | User ID spoofing | strong identity assertion|
| SF +---------------------+--------------------------+
| | Forged 200 Response | TLS, TCP, ingress filt. |
| +---------------------+--------------------------+
| | Forged 302 Response | TLS, TCP, ingress filt. |
| +---------------------+--------------------------+
| | Forged 404 Response | TLS, TCP, ingress filt. |
| +---------------------+--------------------------+
| | Flooding attack | reliable border element |
| | | pooling, rate limit |
| +---------------------+--------------------------+
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| | Session black | DNSSEC |
| | holing | |
| +---------------------+--------------------------+
| | SIP fuzzing attack | border element hardening |
+--------+---------------------+--------------------------+
| | Eavesdropping | SRTP |
| +---------------------+--------------------------+
| | Media Hijack | SRTP |
| +---------------------+--------------------------+
| MF | Media session | SRTCP |
| | tear-down | |
| +---------------------+--------------------------+
| | QoS degradation | SRTCP |
| +---------------------+--------------------------+
| | Malformed messages | border element hardening |
| +---------------------+--------------------------+
| | Messages flooding | rate limit |
+--------+---------------------+--------------------------+
4.1. Current Deployment of Countermeasures
At the time of writing this document not all suggested
countermeasures are widely deployed. In particular, the following
measures to prevent attacks suggested in section Section 3 have not
seen wide deployment:
o DNSSEC
o Digest authentication on all requests in peering agreements
Nevertheless, these protocols and solutions can provide effective
means for preventing some of the attacks with respect to the
SPEERMINT architecture described in this document. It is envisioned
that these countermeasures will be more widely deployed in the
future. Therefore, these mechanisms are listed in this document even
though they are not widely deployed today.
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5. Conclusions
This memo presented the different SPEERMINT security threats
classified in groups related to the LUF, LF, SF and MF respectively.
The multiple instances of the threats are presented with a brief
explanation. Afterwards the suggested countermeasures for SPEERMINT
were outlined together with possible mitigation of the existing
threats by means of them.
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6. Security Considerations
This memo is entirely focused on the security threats for SPEERMINT.
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7. Acknowledgements
This memo takes inspiration from VOIPSA VoIP Security and Privacy
Threat Taxonomy. The authors would like to thank VOIPSA for having
produced such a comprehensive taxonomy which is the starting point of
this draft. The authors would also like to thank Cullen Jennings for
the useful slides presented at the VoIP Management and Security
workshop in Vancouver. Further, the authors thank Hendrik Scholz for
providing extensive and very helpful comments to this draft.
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8. Informative References
[refs.voipsataxonomy]
Zar, J. and et al, "VOIPSA VoIP Security and Privacy
Threat Taxonomy", October 2005.
[refs.speermintarch]
Penno, R., Malas, D., Khan, S., and A. Uzelac, "SPEERMINT
Peering Architecture",
draft-ietf-speermint-architecture-04.txt (work in
progress), August 2007.
[refs.zrtp]
Zimmermann, P., Johnston, A., and J. Callas, "ZRTP:
Extensions to RTP for Diffie-Hellman Key Agreement for
SRTP", draft-zimmermann-avt-zrtp-04.txt (work in
progress), July 2007.
[refs.tlsbis]
Dierks, T. and E. Rescorla, "The TLS Protocol Version
1.2", draft-ietf-tls-rfc4346-bis-09.txt (work in
progress), February 2008.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004.
[RFC4474] Peterson, J. and C. Jennings, "Enhancements for
Authenticated Identity Management in the Session
Initiation Protocol (SIP)", RFC 4474, August 2006.
[I-D.ietf-speermint-terminology]
Malas, D. and D. Meyer, "SPEERMINT Terminology",
draft-ietf-speermint-terminology-16 (work in progress),
February 2008.
[I-D.ietf-speermint-requirements]
Mule, J., "SPEERMINT Requirements for SIP-based Session
Peering", draft-ietf-speermint-requirements-06 (work in
progress), July 2008.
[refs.dbsec]
Gertz, M. and S. Jajodia, "Handbook of Database Security".
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
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[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005.
[RFC3323] Peterson, J., "A Privacy Mechanism for the Session
Initiation Protocol (SIP)", RFC 3323, November 2002.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999.
[refs.tcp-scalability]
Shemyak, K., "Scalability of TCP Servers, Handling
Persistent Connections".
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000.
[RFC3324] Watson, M., "Short Term Requirements for Network Asserted
Identity", RFC 3324, November 2002.
[RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private
Extensions to the Session Initiation Protocol (SIP) for
Asserted Identity within Trusted Networks", RFC 3325,
November 2002.
[RFC3893] Peterson, J., "Session Initiation Protocol (SIP)
Authenticated Identity Body (AIB) Format", RFC 3893,
September 2004.
[RFC3237] Tuexen, M., Xie, Q., Stewart, R., Shore, M., Ong, L.,
Loughney, J., and M. Stillman, "Requirements for Reliable
Server Pooling", RFC 3237, January 2002.
[refs.protos]
Wieser, C., "SIP Robustness Testing for Large-Scale Use".
[RFC4475] Sparks, R., Hawrylyshen, A., Johnston, A., Rosenberg, J.,
and H. Schulzrinne, "Session Initiation Protocol (SIP)
Torture Test Messages", RFC 4475, May 2006.
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Authors' Addresses
Saverio Niccolini
Network Laboratories, NEC Europe Ltd.
Kurfuersten-Anlage 36
Heidelberg 69115
Germany
Phone: +49 (0) 6221 4342 118
Email: saverio.niccolini@netlab.nec.de
URI: http://www.netlab.nec.de
Eric Chen
Information Sharing Platform Laboratories, NTT
3-9-11 Midori-cho
Musashino, Tokyo 180-8585
Japan
Email: eric.chen@lab.ntt.co.jp
URI: http://www.ntt.co.jp/index_e.html
Jan Seedorf
NEC Laboratories Europe, NEC Europe Ltd.
Kurfuersten-Anlage 36
Heidelberg 69115
Germany
Phone: +49 (0) 6221 4342 221
Email: seedorf@nw.neclab.eu
URI: http://www.nw.neclab.eu
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